Lens guide arrangement and apparatus for grinding and polishing toric lenses

ABSTRACT

The invention relates to a guide arrangement for an apparatus for grinding and polishing of a toric lens. A tool is used which is guided in an arrangement comprising a stack of elements including intermediate and end elements each element being articulated on the adjacent element or elements, the articulation or joint axes of an element with the element above or the element below being perpendicular. The joints are of a type of which the wear only causes the elements to be brought closer together in the axis of the stack. The invention is applicable both to machines having a rotating turntable and to machines having a fixed plate.

0 1 31 linited States atent 1191 1111 3,827,192 Ferrand Aug. 6, 1974 LENS GUIDE ARRANGEMENT AND 839,345 12/1906 Wagner 51/124 L APPARATUS FOR GRINDING AND 1,135,936 4/1915 Edmondson 51/124 L 2,179,088 11/1939 Goddu et al. 51/124 L POLISHING TORIC LENSES 2,871,626 2/1959 Desiato 51/124 L [75] Inventor; Jan Fen-and, Puteaux, France 3,577,690 5/1971 Catron 51/284 [73] Assignee: Societe C.M.V., Puteaux, France Primary Examiner A| Lawrence Smith [22] Filed; June 20, 1972 Assistant Examiner-Nicholas P. Godici pp NO: 264,647 Attorney, Agent, or FzrmBre1tenfeld & Levme [57] ABSTRACT [30] Foreign Application Priority Data The invention relates to a guide arrangement for an June 21 1971 France 71.22417 apparatus f r grinding and polishing of a toric lens. A

tool is used which is guided in an arrangement com- [52] 11.8. C1 51/124 L, 51/216 LP pri ing a ta k of elements including intermediate and [51] Int. Cl B24b 13/02 nd l ments a h lement being articulated 0n the [58] Field at Search 51/124 L, 124 R, 216 L, adjacent element or elements, the articulation or joint 51/216 R, 217 L, 217 R, 162, 284, 101 LG, axes of an element with the element above or the ele- 277 ment below being perpendicular. The joints are of a type of which the wear only causes the elements to be [56] 4 References Cited brought closer together in the axis of the stack. The UNITED STATES PATENTS invention is applicable both to machines having a ro- 646,672 4/1900 Wagner 51/124 L mung turntable and to machmes having a fixed plate 720,509 2/1903 Wells 51/124 L 10 Claims, 4 Drawing Figures PMENTED nus 51974 SHEET 1 (IF 3 PATENTEU G 6 74 SHEEI 2 OF 3 LENS GUIDE ARRANGEMENT AND APPARATUS FOR GRINDING AND POLISHING TORIC LENSES BACKGROUND OF THE INVENTION The present invention relates to a guide arrangement for a grinding and polishing tool for toric lenses, with which it is possible to work singly or using a wheel.

Toric lenses are those that comprise a surface of which the sections through two characteristic perpendicular planes are arcs of circles of different radii. Grinding and polishing of toric lens blanks are carried out by tools which have a corresponding continuous or divided toric surface. The actual surface of these'tools also have sections through two characteristic perpendicular planes which are arcs of circles of different radii.

It is essential that the above mentioned two sections are truly perpendicular, especially in the case of corrective lenses. It is thus essential that, during grinding and polishing, the two characteristic perpendicular planes of the grinding or polishing tool extending through one point of the lens surface always remain parallel to themselves. Consequently, the grinding and polishing apparatus must use a tool which is given varied movements, but without involving any rotation about an axis perpendicular to the toric surface.

The grinding and polishing apparatus for toric lenses thus comprise a guide arrangement which prevents these rotations and a drive means ensuring the displacement of the tool relative to the toric lens. The drive means generally comprises a ball joint, to the axis of which is exerted the force for applying the tool to the lens and which transmits perpendicularly of its axis various movements which ensure the relative displacement of the lens and the tool.

Numerous guide arrangements which function in accordance with the principle as described above are known.

Among the known guide arrangements for working singly, arrangements are known in which the lens or the tool is fixed, while the other element, i.e., the tool or the lens respectively, is guided by forks, rods and/or joints, particularly ball joints. However, it is to be noted that the guide arrangements using a fork present a slight offsetting, which is harmful to the precise formation of the torus.

In other arrangements, the lens or the tool is driven in rotation, while the other element, i.e., the tool or the lens respectively, is guided by an arrangement which itself also comprises forks, rods and/or joints.

In apparatus for grinding and polishing on the wheel, the guide arrangements which are used are similar, that is to say, they also comprise forks, rods and/or joints.

All these arrangements when they are correctly adjusted enable toric surfaces of good quality to be obtained. Nevertheless, all these mechanical guide arrangements are exposed at least in part to the abrasive which is used for the grinding or polishing, and it follows that there is rapid wear. The wear in the known arrangements has the-disadvantage of causing play in the joints, and this play introduces a certain relative displacement of the two arcuate sections of the lens, which sections become less well defined and may no longer be perpendicular. This play appears in all the types of joints, particularly joints which comprise bearings and forks. Hence, a small amount of wear in the known guide arrangements produces an alteration of the characteristics of the surface of the lens which is obtained.

An object of the present invention is to reduce or obviate this disadvantage by providing a guide arrangement which ensures constancy in the characteristics of the lenses which are produced, even with a very pronounced wear in the guide arrangement.

Another object of the invention is to provide a guide means which can serve equally well for working on turntable or wheel type grinding and polishing arrangements.

Accordingly, the invention proposes an arrangement which the wear on the joints only produces play in a direction substantially perpendicular to the toric surface, thereby making it possible always to keep equal the perpendicular relationship of the two planes containing the arcuate sections.

BRIEF SUMMARY OF THE INVENTION According to the invention there is provided a guide arrangement for a grinding and polishing tool for toric lenses, comprising a stack of elements including intermediate elements and end elements, and articulated joints, each element being articulated on the adjacent element or elements, the joint axis of one element with the upper adjacent element being perpendicular to its joint axis with the lower adjacent elements, the joints being of a type of which the wear only causes the elements to be brought closer together in the axis of the stack.

According to one preferred embodiment, the guide arrangement according to the invention comprises five elements articulated about four joint axes. The three intermediate elements are rings which comprise on one face two male joint portions and on an opposite face two female joint portions, the axis defined by the male joint portions being perpendicular to the joint axis defined by the female joint portions. Preferably, one of the end elements is a ring carrying two joint portions on one of its faces, the other end element being a crosshead which serves as a support for the tool or the blank and comprising a central articulation point.

The arrangement preferably comprise compensating means by which it is possible to change the height of the stack when the arrangement has been subject to a certain amount of wear.

Advantageously the joints are formed either by protuberances on an axis parallel to the stack axis, comprising a spherical end co-operating with cones, or knife-edges co-operating with V-shaped grooves, of which the edges are aligned.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view in section of one embodiment of guide arrangement according to the invention, the sectional plane passing through the axis of the stack.

FIG. 2 is a diagrammatic representation of a driving arrangement.

FIG. 3 represents a partial diagram of a second embodiment having a support in the form of a wheel.

FIG. 4 is a view in section of the guide arrangement, this view being orthogonal with respect to the view designated as FIG. 1.

DESCRIPTION OF PREFERRED EMBODIMENTS The apparatus used for grinding and polishing of a blank 1 comprises a rotating plate or turntable 2, the mechanism of which is protected by a suitably shaped sleeve 3, and a driving point 4.

The guide arrangement comprises an end element 5, three intermediate elements in the form of rings 6, 7 and 8, and a crosshead 9 as upper end element. The lower end element comprises a support 10 and a ring 11. The support 10 co-operates by means of a bore 12 with the upper part of the turntable 2 of the apparatus. The support is provided on its upper part with a dovetailed groove 13 which permits a polishing or grinding tool 14 to be fixed in position.

The ring 11 is able to slide along the support 10 and is held relative to the support 10 by pins 15. These pins 15 are fixed in the ring 11 and co-operate for sliding movement with bores 16 carried by the support 10 so as to prevent turning movements of the ring 11 about the support 10, while permitting its longitudinal displacement. A stack of resilient washers 17 provides a latitude in the adjustment of the distance between the support 10 and the ring 11.

As shown in orthogonally related FIGS. 1 and 4 rings 11 and 6, 6 and 7, 7 and 8, and the ring 8 and the crosshead 9, each co-operate with one another by an articulation about axes defined by two ball joints. The joint axis 40 (see FIG. 4) of the rings 1 l and 6 is perpendicular to the joint axis 41 (see FIG. 1) of the rings 6 and 7, which is itself perpendicular to the joint axis 42 (see FIG. 4) of the rings 7 and 8, this latter axis being itself perpendicular to the joint axis 43 (see FIG. 1) of the ring 8 and the crosshead 9.

All these articulations are carried out about two identical ball joints, of which the male element is carried on the upper face of a ring and of which the female element is carried by the lower face of a ring or of the crosshead. Each ring comprises two diametrically opposed ball joints.

The ball joints defining the different articulation axes 40-43 are all identical. They each comprise a spherical male element 18 carried by the lower plate and a conical female element 19 carried by the upper plate or the crosshead. The elements 18 and 19 are maintained in the rings or the crosshead by cylindrical parts 20 cooperating with bores 21 in the rings or the crosshead. These cylindrical parts are held in position by screws 22. Two adjacent articulated elements are held close to one another by causing the spherical elements 18 to cooperate with the conical elements 19 by means of springs 23.

The crosshead 9 comprises an ofiset central part 24 serving as a support for the blank. The blank 1 is fixed by wax 25 on a support 26 screwed into the crosshead 9. Rotational movement of the support 26 relatively to the crosshead 9 is prevented by a pin 27. The support 26 carries a female cone 28 for co-operating with the point 4 of the grinding and polishing apparatus.

The operation of the arrangement as described is as follows. The turntable 2 is given a rotational movement and drives the tool 14 with a continuous movement. The point 4 exerts a downwardly directed force, the value of which is adjustable, and exerts transverse forces which impose linear, circular or planetary displacements on the end of the point. The guide arrangement which is fixed on the turntable 2, turns at the same time as the tool 14, driving the blank 1 at the same speed of rotation.

The point 4 causes the crosshead 9 to be displaced transversely relatively to the tool, but the guide arrangement prevents all relative rotation of the blank 1 and the tool 14.

The positioning of the tool and the blank is very simple. It is possible to withdraw either the upper crosshead, which then frees the interior of the guide arrangement, or to withdraw the guide arrangement, which then frees the turntable 2.

The male and female elements of the ball joints 18 and 19 are preferably made of tungsten carbide, although this is not essential as the wear on the ball joints in'fact only causes a reduction in the height of the stack. This reduction in height can be compensated for by modifying the stack of washers 17 between the support 10 and the ring 11.

The arrangement described permits work to be carried out under correct mechanical conditions, because it is possible to bring the head of the point 4 very close to the surface during grinding or polishing. The arrangement described can be mounted on all machines comprising a turntable or a fixed plate and a point.

With a few modifications obvious to the person skilled in the art, it can also be mounted on the known wheel-type grinding and polishing arrangements. These modifications only apply to the end element placed facing the point.

It is obvious that various modifications can be made to the embodiment described. In particular, the ring form of the intermediate element and the arrangement of the upper crosshead have only been mentioned by way of example. Similarly, the ball joints can be replaced by joints of a different type and may in particular comprise knife-edges co-operating with V-shaped grooves.

FIG. 2 shows a spindle 29 which is rotated by a motor 30 and which carries at one end the driving arrangement for the guide means (only the head of the point 4 of the driving means has been shown, the other end of the spindle receiving a pneumatic, hydraulic or mechanical pressure from a pressure-applying arrangement 31). Thus, the pressure applying arrangement urges point 4 into the cone 28 and motor 30 rotates point 4 against the cone 28.

FIG. 3 shows a support 32 in the form of a wheel or drum, which carries on its periphery the elements 1 which are to be ground and polished. This support, which may or may not be given a rotational movement about the axis 33 of the wheel, is in the form of a barrel or cylinder, permitting the grinding and polishing of several elements which pass in succession before the tool shown diagrammatically at 14. It will be understood that the barrel or the tool is guided by an arrangement in accordance with the present invention, which has not been shown in this Figure.

What we claim is:

1. An arrangement for grinding and polishing a toric lens, comprising a. a support for holding a grinding or polishing tool,

b. means for rotating said tool support about an axis of rotation; c. a support for holding a lens,

d. a guide arrangement for supporting and transmitting to said lens support the rotary motion of said rotating means,

e. said guide arrangement comprising a plurality of rigid elements stacked one upon another along said axis of rotation, said elements including two end elements and at least one intermediate element between said end element, and joint means between each two successive elements in the stack, each intermediate element being articulated to the element directly below it by two joint means arranged on a first line perpendicular to said axis of rotation and on opposite sides of said axis of rotation, said joint means thereby defining a first pivot axis perpendicular to said axis of rotation, each intermediate element being articulated to the element directly above it by two other joint means arranged on a second line perpendicular to said axis of rotation and on opposite sides of said axis of rotation, said second line also being perpendicular to said first line, said other joint means thereby defining a second pivot axis perpendicular to both said axis of rotation and to said first pivot axis, whereby said lens support is permitted to move laterally or in a planetary motion with respect to said tool support but said supports cannot rotate with respect to each other, and

f. means for applying a force to said lens support in the direction of said tool support.

2. An arrangement according to claim 1, comprising five elements which are articulated about four joint axes.

3. An arrangement according to claim 2, in which the three intermediate elements are rings which comprise on one face two male joint parts and on an opposite face two female joint parts, the axis defined by the male joint parts being perpendicular to the axis defined by the female joint parts, one of the end elements being a ring carrying two joint parts on one of its faces.

4. An arrangement according to claim 3, in which the other end element is a crosshead serving as a support for the grinding or polishing tool for the lens and comprising grinding or polishing apparatus and a central articulation point capable of co-operating with the driving point of the grinding or polishing apparatus.

5. An arrangement according to claim 1, in which one of the elements, comprises means for compensation of wear, permitting the height of the stack to be increased.

6. An arrangement according to claim 5 in which the said one of the elements is an end element.

7. An arrangement according to claim 1 which is actuated by a device comprising a spindle driven in rotation by a motor and to one end of which a pressure is applied.

8. An arrangement according to claim 1 wherein each joint means articulating one element to an adjacent element comprises a male joint part on one element and a female joint part on the adjacent element.

9. An arrangement according to claim 8 in which at least some male joint parts are studs or projections comprising a spherical end co-operating with conical female joint parts.

10. An arrangement according to claim 8, in which at least some male joint parts are knife-edges cooperating with female joint parts comprising V-shaped grooves, the edges of the knife-edges and the grooves being aligned. 

1. An arrangement for grinding and polishing a toric lens, comprising a. a support for holding a grinding or polishing tool, b. means for rotating said tool support about an axis of rotation; c. a support for holding a lens, d. a guide arrangement for supporting and transmitting to said lens support the rotary motion of said rotating means, e. said guide arrangement comprising a plurality of rigid elements stacked one upon another along said axis of rotation, said elements including two end elements and at least one intermediate element between said end element, and joint means between each two successive elements in the stack, each intermediate element being articulated to the element directly below it by two joint means arranged on a first line perpendicular to said axis of rotation and on opposite sides of said axis of rotation, said joint means thereby defining a first pivot axis perpendicular to said axis of rotation, each intermediate element being articulated to the element directly above it by two other joint means arranged on a second line perpendicular to said axis of rotation and on opposite sides of said axis of rotation, said second line also being perpendicular to said first line, said other joint means thereby defining a second pivot axis perpendicular to both said axis of rotation and to said first pivot axis, whereby said lens support is permitted to move laterally or in a planetary motion with respect to said tool support but said supports cannot rotate with respect to each other, and f. means for applying a force to said lens support in the direction of said tool support.
 2. An arrangement according to claim 1, comprising five elements which are articulated about four joint axes.
 3. An arrangement according to claim 2, in which the three intermediate elements are rings which comprise on one face two male joint parts and on an opposite face two female joint parts, the axis defined by the male joint parts being perpendicular to the axis defined by the female joint parts, one of the end elements being a ring carrying two joint parts on one of its faces.
 4. An arrangEment according to claim 3, in which the other end element is a crosshead serving as a support for the grinding or polishing tool for the lens and comprising grinding or polishing apparatus and a central articulation point capable of co-operating with the driving point of the grinding or polishing apparatus.
 5. An arrangement according to claim 1, in which one of the elements, comprises means for compensation of wear, permitting the height of the stack to be increased.
 6. An arrangement according to claim 5 in which the said one of the elements is an end element.
 7. An arrangement according to claim 1 which is actuated by a device comprising a spindle driven in rotation by a motor and to one end of which a pressure is applied.
 8. An arrangement according to claim 1 wherein each joint means articulating one element to an adjacent element comprises a male joint part on one element and a female joint part on the adjacent element.
 9. An arrangement according to claim 8 in which at least some male joint parts are studs or projections comprising a spherical end co-operating with conical female joint parts.
 10. An arrangement according to claim 8, in which at least some male joint parts are knife-edges co-operating with female joint parts comprising V-shaped grooves, the edges of the knife-edges and the grooves being aligned. 